1. Field of the Invention
The present invention relates to an engine for vehicle including a crankcase and a starting system having a starting motor arranged above a top wall of the crankcase and a starting gear train for transmitting rotating power of the starting motor to a crankshaft.
2. Description of the Related Art
As a related art of such engine for vehicle, Japanese Patent Application Laid-Open (JP-A) No. 2006-226258 discloses an engine for a motorcycle having a starting system as shown in FIG. 8. In FIG. 8, a starting motor 201 is arranged above a top wall of a crankcase 200. An output gear (output pinion) 202 of the starting motor 201 is connected with a crankshaft 203 via a starting gear train and a one-way clutch 210 so as to transmit rotating power of the starting motor 201 to the crankshaft 203. The starting gear train has a plurality of starting idle gears 205, 206 and a starting gear 207 on the crankshaft 203.
A starting gear chamber 212 for housing the starting gear train is surrounded by a first starting gear chamber cover 214 fastened to an end face of the crankcase 200 in a crankshaft axial direction and a second starting gear chamber cover 215 fastened to the first starting gear case cover 214.
Both the starting gear chamber covers 214, 215 are protruded upward from the top wall of the crankcase 200. The upward protruded portion of the first starting gear chamber cover 214 has a cylindrical motor mounting hole 220 in parallel with the crankshaft 203. A cylindrical end 222 is formed on an output gear side of the starting motor 201 and fitted in the motor mounting hole 220. Another end 223 of the starting motor 201 on the opposite side of the output gear side is fastened to a mounting portion 224 formed on the top wall of the crankcase 200 by a bolt 225 or the like.
The starting gear train has two starting idle shafts 230, 231. The starting idle gears 205, 206 are rotatably supported by the starting idle shafts 230, 231, respectively. The starting idle gears 205, 206 have large-diameter gear portions 205a, 206a and small-diameter gear portions 205b, 206b, respectively. The large-diameter gear portion 205a of the upper starting idle gear 205 is engaged with the output gear 202 of the starting motor 201. The small-diameter gear portion 205b of the upper starting idle gear 205 is engaged with the large-diameter gear portion 206a of the lower starting idle gear 206. The small-diameter gear portion 206b of the lower starting idle gear 206 is engaged with the starting gear 207. The starting gear 207 is coupled to the crankshaft 203 via the one-way clutch 210 and transmits only starting power from the starting motor 201 to the crankshaft 203.
As another related art, Japanese Patent Application Laid-Open (JP-A) No. 2000-120515 discloses an engine for vehicle including a motor mounting hole formed in a top wall of an upper crankcase member of a crankcase of the engine.
In the related art in FIG. 8, the motor mounting hole 220 is formed in the first starting gear chamber cover 214 separated from the crankcase 200, and the cylindrical end 222 on the output gear side of the starting motor 201 is fitted in the motor mounting hole 220. Therefore, the starting motor 201 is located at a position greatly displaced toward the starting gear case 212 in the crankshaft direction. The starting gear case 212 is protruded outwardly of the crankshaft direction. The size of the engine in the engine width direction (the crankshaft direction) is increased. Consequently, the engine becomes larger.
On the other hand, in another related art, since the motor mounting hole is formed in the upper crankcase member, the above problems can be solved. However, another problem is occurs, for example, it takes long time to form the motor mounting hole.